Plastic Injection Molding

Plastic Injection Molding

The Plastic Injection Molding process is the most common manufacturing technique for making plastic materials. It is used for the majority (35 percent) of plastic products, ranging from automotive dashboards to bottle caps and pocket combs.  Starting in the 1930s, plastic injection molding is used for mass production and prototyping, and is commonly used in the food service, medical, computer and automotive industries.  Most molded plastic products are made from thermoplastics, which become pliable when heated and rigid when cooled.  Plastic Injection Molding has many advantages, including high production rates and low labor costs.  There is little waste produced during this process, and it may be recycled easily.

Producing plastics through Injection Molding is a 4 step process.  First, the 2 halves of the injection mold are clamped hard under pressure.  The plastic, usually in pellet form, is then loaded through a hopper and heated to molten form and injected into the mold, which is an inverse of the desired shape of the part being made.  The plastic is then left for a short time to cool, and ejected out of the machine with force, as the plastic tends to shrink and stick to the mold.

If plastic injection molding fits the manufacturer's need better than alternatives such as blow molding (for hollow objects) or thermal molding (which saves energy), they then need to choose what type of plastic injection molding to use.  Cold runner molding is for simple parts or those with more than one color, hot runner molding is the most inexpensive option, and insulated runner molding is best for a large number of parts which are needed quickly.

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